This invention relates to a lubricating oil supplying device for an engine and more particularly to an improved lubricating pump for a machine such as an engine.
One form of lubricating system employed within internal combustion engines and particularly two cycle engines employs a reciprocating plunger type pump that is driven by the engine and supplies a finite amount of lubricant during each stroke of the pump. Of course, it is desirable to vary the output of the pump or the amount of lubricant delivered to the engine during each pump stroke so as to insure against excess lubrication and the disadvantages accompanying it. That is, it is desirable to insure against the supply of excess lubricant so as to avoid exhaust smoke and the emission of unburned hydrocarbons. A number of arrangements have been employed for controlling the amount of lubricant delivered to the engine during each pumping stroke.
One way in which the amount of lubricant may be controlled is by changing the effective stroke of the plunger. This has conventionally been done in the past by providing some form of adjustable stop that cooperates with a portion of the plunger which is always exposed from the bore in which the plunger reciprocates. There are a number of disadvantages to such an arrangement.
One disadvantage with this type of arrangement is that the clearance volume of the pump at top dead center of the plunger will then vary as the amount of lubricant pump is changed. That is, as the plunger stroke is adjusted, the clearance volume increases as the amount of lubricant is decreased. Having large clearance volumes presents a number of disadvantages. The primary disadvantage is that the larger the clearance volume, the more likely it is for air to be drawn into the pumping chamber during operation. This will give rise to variations in the amount of lubricant actually delivered and a decrease in the effectiveness of the pump.
In addition, with this type of pumping mechanism the plunger is supported in a blind bore. Therefore, it is necessary to provide some clearance at the end of the plunger stroke, even when the maximum amount of lubricant is being delivered. This must be done to insure against interference between the head of the plunger and the blind end of the bore. Thus, it is not possible under any condition to maintain minimum clearance volume with this type of pump stroke adjustment.
It is, therefore, a principal object of this invention to provide an improved arrangement for varying the output of a reciprocating plunger type of pump without changing the clearance volume of the pump at top dead center.
It is a further object of this invention to provide an improved arrangement for controlling the pumping stroke of a plunger type pump while maintaining zero clearance volume at top dead center regardless of the amount of lubricant being pumped.
It is a further object of this invention to provide an improved plunger type of lubricant pump wherein the plunger can reciprocate in an open as opposed to a blind bore.
The quantity of lubricant delivered to the engine is normally varied in response to an engine condition, most typically engine speed. The conventional types of systems, including those of the prior art as previously mentioned, adjust the stroke of the pump plunger in response to the setting of the speed controlling unit of the engine, such as the throttle valve. Normally this is done by providing a mechanical connection between the throttle valve or its controlling mechanism and the stop which changes the plunger stroke. As a result, these devices generally vary the amount of lubricant linearally with respect to engine speed. Devices have been incorporated, however, for changing this linearity somewhat in response to transient conditions, but the overall control is generally linear. However, the lubricant demands of the engine are not always linearally related to the engine condition.
It is, therefore, a further principal object of this invention to provide an arrangement for varying the amount of lubricant pumped to an engine in response to a condition of the engine without sensing directly that condition or the control for that engine condition so as to permit the desired delivery to be achieved.
It is a further object of this invention to provide an arrangement for controlling the amount of lubricant delivered to a machine by a lubricant pump in response to an machine condition without having the amount of lubricant necessarily be supplied in a linear fashion.
Another disadvantage of the type of lubricant control as aforedescribed is that the mechanical connection between the engine speed control and the lubricant pump also gives rise to mechanical loadings in the system which will change the operator's "feel" of the control of which he is attempting to effect. That is, if the pump output is adjusted in response to position of the throttle controlling member, then the feedback from the mechanical control to the pump adjustment will interfere with the operator's feel for the condition of the throttle valve. In addition, such arrangements add to the load which the operator must exert on the control in order to achieve the control of both the engine and the amount of lubricant supplied.
It is, therefore, a further object of this invention to provide an arrangement for controlling the amount of lubricant supplied to a machine in response to a condition of the machine without necessitating a mechanical control to the mechanism which varies the machine condition.
Another disadvantage of the prior art type of systems wherein there is a mechanical connection between the pump output controlling member and the member that controls the engine condition is that the prior art devices generally can vary the amount of lubricant only with respect to that particular condition. For example, if the control is related to the engine throttle control, then the devices generally can vary the amount of lubricant only in response to throttle control position. However, the amount of lubricant required by the engine may vary in response to other conditions than merely throttle position. Although the prior art mechanisms have permitted some minor adjustment, primarily for transient conditions, they have not been able to accommodate changes in lubrication for conditions in addition to the main sensed condition.
It is, therefore, a still further object of this invention to provide an arrangement for controlling the amount of lubricant supplied to an engine in response to engine speed and another condition, such as temperature.